What had started as a peaceful demonstration Wednesday over the Jan. 1 shooting of Oscar Grant escalated into trouble. At least three cars were set on fire, many other automobiles were damaged, and windows were broken on some downtown stores.

Police in riot gear threw tear gas to try to break up the demonstration. At least 14 people were arrested before the unrest ebbed overnight.

Grant, 22, was killed on a Bay Area Rapid Transit station platform after officers went there amid reports about groups of men fighting on a train. He was one of a small group of men taken off the train, and officers had made him lie face down at the time he was killed.

The shooting and events leading up to it were captured on amateur videos that have been broadcast on television.

Officer Johannes Mehserle resigned from the transit agency shortly before he was supposed to be interviewed by investigators Wednesday. Mehserle’s attorney did not immediately respond to calls for comment Wednesday.

Grant’s family has filed a $25 million wrongful death claim against BART and want prosecutors to file criminal charges against Mehserle.

Dellums went to the protest scene Wednesday night to urge for calm. He and several council members then led a group toward City Hall and further addressed them.

“Even with our anger and our pain, let’s still address each other with a degree of civility and calmness and not make this tragedy an excuse to engage in violence,” Dellums said. “I don’t want anybody hurt, I don’t want anybody killed.”

Dellums had directed the city’s police department to conduct a third investigation into Grant’s killing and to treat the incident as a homicide.

During the protest, some people threw bottles, a window of a fast-food restaurant and other downtown stores were smashed. Police in riot gear threw tear gas to try to break it up.

“The crowd started to become more agitated, more hostile, started throwing stuff at the police,” Oakland police spokesman Jeff Thomason said. “We gave a dispersal order four to five times over a 20-minute period, then we had our officers go in and start making arrests.”

Police didn’t immediate respond to a request early Thursday for an update on the number of arrests.

Organizers of the protest say they have another rally set for later Thursday during a BART board meeting.